In the field of manufacturing devices, lithography is often used. The process is a pattern transferring process that is used to generate features of desired shape and size. The process begins with coating a layer of resist on a substrate. Thereafter, a mask having desired pattern is disposed upstream of the resist. A radiation source is disposed upstream of the mask, and the radiation from the radiation source is directed toward the resist through the mask. The mask comprises one or more transparent areas through which the radiation may pass, and one or more opaque areas that block the radiation. The portion of the resist exposed to the radiation is cured and hardened, whereas the portion not exposed to the radiation remains uncured. The uncured portion is then removed exposing a portion of the substrate thereunder. As a result, the pattern of the mask is transferred onto the resist.
The pattern is then transferred to the substrate using wet or dry etching process. For example, the exposed portion of the substrate is etched with etchant, whereas the portion of the substrate covered with the resist structure may remain unetched. As a result, the pattern of the resist structures may be transferred onto the substrate.
This pattern transferring process is an important process in manufacturing semiconductor devices with high circuit density. By manipulating the radiation, the mask, and the resist, a substrate with sub-micron patterns may be generated. However, this process requires complex and costly optical systems for precise manipulation of the radiation. With the wavelength of the radiation used in device manufacturing continually decreasing, manipulation of such radiation has become more costly and difficult.
In response, less complex and less costly nano-imprint lithography has been developed. In this lithography process, a substrate 102 is coated with resist 112, as shown in FIG. 1A. Thereafter, a mold 122 (FIG. 1B) having a desired pattern may be pressed against the substrate 102 (FIG. 1C). The mold 122 may comprise a base 122a and a plurality of protrusions 122b that are spaced apart by recess 122c. While the mold 122 is pressed against the substrate 102, the resist 112 is exposed to the radiation 132 and cured (FIG. 1C). By curing the resist 112 while the mold is pressed, a pattern reflective of that in the mold 122 may be formed on the resist 112 (FIG. 1D). The mold 122 is subsequently removed, and the resulting substrate 102 may be etched according to the pattern of the resist 112 (FIG. 1E). Thereafter, the resist structure 112a remaining on the substrate 102 may be removed (FIG. 1F).
Although the nano-imprint lithography may be a cost effective process, the shape of the image or pattern that can be formed in the substrate using the process is limited. As such, a new process for forming structures is needed.